The science is clear and convincing that climate change is happening, happening rapidly, and happening primarily because of human activities. Every weather event that happens nowadays takes place in the context of the changes in the background climate system. Globally, the temperatures are higher, the sea level is higher, and there is more water vapor in the atmosphere, which energizes storms. The background atmosphere has changed and continues to change because of the changing climate. The U.S. National Climate Assessment (NCA) is being conducted under the auspices of the Global Change Research Act of 1990 that requires a report to the President and the Congress every four years that integrates, evaluates, and interprets the state of the science and the potential effects of global change on the natural environment, agriculture, energy production and use, land and water resources, transportation, human health and welfare, human social systems, and biological diversity. National climate assessments act as status reports about climate change science and impacts. The NCA is aimed at informing the nation about already observed changes, the current status of the climate, and anticipated trends for the future. The NCA report process integrates scientific information from multiple sources and sectors to highlight key findings and significant gaps in our knowledge. The report just went out for public review; the final version will be published in December or next January. This presentation summarizes the ongoing NCA activities and provides a discussion of the current understanding of the science of climate change, with a special emphasis on some of the issues facing the Midwest.